US6104182A - Method of deriving a signal indicating an oscillation in an electric power supply system - Google Patents

Method of deriving a signal indicating an oscillation in an electric power supply system Download PDF

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US6104182A
US6104182A US09/170,889 US17088998A US6104182A US 6104182 A US6104182 A US 6104182A US 17088998 A US17088998 A US 17088998A US 6104182 A US6104182 A US 6104182A
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positive sequence
sequence system
values
forming
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Andreas Jurisch
Micheal Schwenke
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00—Arrangements for measuring electric power or power factor
    • G01R21/10—Arrangements for measuring electric power or power factor by using square-law characteristics of circuit elements, e.g. diodes, to measure power absorbed by loads of known impedance
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency

Definitions

  • the present invention relates to a method for deriving a signal (e.g., oscillation signal) indicating oscillation in an electric power supply system.
  • a signal e.g., oscillation signal
  • German Patent Application No. 195 03 626 describes a conventional method where impedance values are formed from current and voltage sampling values at predetermined intervals in response to an excitation. The size of its change in time is determined from the first impedance value falling in an oscillation polygon and from the preceding impedance value, and a suspected oscillation signal is generated when the change is below a predetermined limit value. If an impedance value falling in the triggering polygon of an impedance protection is obtained in further review of the impedance values, the oscillation signal is generated if the suspected oscillation signal still exists. Oscillations with a frequency up to 1 Hz at most can be detected by this method.
  • German Patent No. 41 00 646 describes a method and an arrangement for protecting impedance protection devices from unwanted tripping during transient power oscillations where at least one blocking signal is generated for the impedance protection device by time derivation of a power-based electric quantity, and unwanted tripping of the impedance protection device is prevented by using an impedance locus diagram, but the resulting changes in active power and reactive power are related to the apparent power after forming the difference, and this quotient is used to form an oscillation signal.
  • An object of the present invention is to provide a method for obtaining an oscillation signal with which higherfrequency oscillations can be detected.
  • current and voltage space vectors of the positive phase-sequence system of the power supply system are formed according to the present invention from the phase current and voltage sampling values.
  • a positive sequence system active power quantity which is proportional to the instantaneous value of the active power of the positive sequence system, is formed together with a reactive power quantity of the positive sequence system which is proportional to the reactive power of the positive sequence system.
  • system frequency components are eliminated from the positive sequence system active power quantity, thus forming an active power measured quantity, and, from the positive sequence system reactive power, forming a reactive power measured quantity.
  • a current quantity of the positive sequence system is formed from the current space vectors of the positive sequence system.
  • a measured current quantity of the positive sequence system is formed from the current quantity of the positive sequence system by a least-squares estimate. Resistance values of the positive sequence system are obtained by forming the quotient of the measured active power quantity and the squared measured current quantity of the positive sequence system. Reactance values of the positive sequence system are obtained by forming the quotient of the measured reactive power quantity and the squared measured current quantity of the positive sequence system. Chronologically successive impedance values of the positive sequence system formed from resistance and reactance values of the positive sequence system correlating with one another in time are subjected to a check for monotony and a check for sudden changes. If they are found to be monotonic and without sudden changes, a suspected oscillation signal is formed.
  • a circle center point of a trajectory formed by impedance values of a positive sequence system with respect to the respective impedance value of the positive sequence system is formed from the impedance values of the positive sequence system by estimation.
  • An oscillation confirmation signal is generated when the imaginary component of the center point of the circle exceeds the absolute value of the positive sequence system reactance value of the respective positive sequence system impedance. If a suspected oscillation signal and an oscillation confirmation signal occur simultaneously, the oscillation signal is formed if the impedance value of the positive sequence system formed last is within the oscillation polygon.
  • One advantage of the method according to the present invention is that it permits rapid detection of oscillations, where the oscillations can be clearly differentiated from three-phase faults.
  • the method according to the present invention makes it possible to detect relatively high-frequency oscillations, even when the load angle changes non-uniformly over time.
  • Another important advantage of the method according to the present invention is that the trajectory formed from chronologically successive positive sequence system impedance values is smoothed very well because of the least squares estimate and thus can be adequately analyzed.
  • chronologically successive positive sequence system resistance values are monitored to advantage for whether a minimum rate of change is maintained when positive sequence system impedance values formed by chronologically correlated positive sequence system resistance and reactance values lie within the oscillation polygon, and the oscillation signal is canceled if the rate is lower than this minimum rate of change.
  • FIG. 1 shows an exemplary embodiment of an arrangement for carrying out a method according to the present invention.
  • FIG. 2 shows a diagram illustrating the method according to the present invention.
  • FIG. 3 shows an impedance locus curve in oscillation states.
  • FIG. 4 shows a diagram illustrating how a circle center of a trajectory of a positive sequence system impedance values is estimated.
  • FIG. 5 shows time curves for the active power and reactive power of the positive sequence system.
  • FIG. 6 shows time curves for the measured active power and measured reactive power of the positive sequence system.
  • FIG. 7 shows a trajectory of the impedance values of the positive sequence system with oscillations after a three-phase fault.
  • FIG. 1 shows a device 3 for forming current and voltage space vectors.
  • the device is connected at the input end to three phases of a three-phase electric power supply line via current and voltage transformers in a manner not shown here.
  • Device 3 for forming space vectors is connected at the output end to a device 4 for forming an active power quantity P' of a positive sequence system, with a least squares estimator 5 connected at the output end downstream from device 4. At its output, least squares estimator 5 is connected to one input of a quotient forming device 6.
  • a device 7 for forming a reactive power quantity Q' of a positive sequence system is also connected to device 3, with another least squares estimator 8 connected downstream from device 7. A measured reactive power Q supplied at the output of this additional estimator 8 is sent via an input to another quotient forming device 9.
  • Current space vector i.sub. ⁇ of device 3 is squared in a squaring element 10 having a downstream summing unit 11.
  • Another squaring element 12 is connected to the input of summing unit 11 and receives at its input additional current space vector i.sub. ⁇ of device 3.
  • a square root extractor unit 13 is connected to the output of summing unit 11 and has a least squares estimator 14 connected downstream.
  • Square root extractor unit 13 generates a positive sequence system quantity i' from which a positive sequence system measured quantity i is formed by least squares estimator 14.
  • Least squares estimator 14 is connected to additional inputs of quotient forming devices 6 and 9 via a squaring element 15.
  • Positive sequence system resistance values Wr are formed by quotient forming device 6 and positive sequence system reactance values Wx are formed by additional quotient forming device 9 and sent to an analyzer unit 16 which delivers, if appropriate, an oscillation signal Sp at its output.
  • Signal Sp can be generated as follows with the arrangement according to FIG. 1:
  • phase currents Ir, Is, It and phase voltages Ur, Us, Ut of the power supply system (not shown; formed by a three-phase power transmission line, for example) are sampled in device 3, forming phase current and phase voltage sampling values ur, us, ut, ir, is and it.
  • an active power quantity P' of the positive sequence system proportional to the instantaneous active power of the positive sequence system is formed from these transformed sampling values and space vectors according to the following equation:
  • the first term in the equation describes a sinusoidal signal component of the active power quantity P' of the positive sequence system, said component oscillating at the system frequency and decaying exponentially over time.
  • the second term describes another signal component of the active power quantity P' of the positive sequence system, the component likewise oscillating at the system frequency and decaying exponentially over time, with the one signal component and the other being orthogonal to one another, because the additional signal component is cosinusoidal.
  • C denotes a component measured value of active power quantity P' of the positive sequence system, the component measured value C oscillating at an oscillation frequency and being dependent on time, and therefore characterizing an instantaneous value.
  • the signal model according to equation (3) is based on the assumption that in a three-phase short-circuit, practically no active power and thus no positive sequence system active power is being converted, so that active power quantity P' of the positive sequence system must drop to a very small value--almost zero--in such a short-circuit. This drop in active power quantity P' of the positive sequence system is taken into account by the first two terms in equation (3).
  • the signal model according to equation (3) also takes into account power oscillations, i.e., through the third term and swing component measured value C. Swing component measured value C takes into account those frequency components in active power quantity P' of the positive sequence system that are below the system frequency and are thus characteristic of system oscillations.
  • Active power quantity P' of the positive sequence system is transmitted to least squares estimator 5 where the system frequency components in active power quantity P' of the positive sequence system are removed and a measured active power quantity P of the positive sequence system is formed.
  • This measured active power quantity P of the positive sequence system corresponds to swing component measured value C of active power quantity P' of the positive sequence system oscillating at an oscillating frequency.
  • measured reactive power quantity Q of the positive sequence system is formed by device 7 and additional least squares estimator 8 from reactive power quantity Q' of the positive sequence system, which is formed according to the following equation (4).
  • Measured reactive power quantity Q of the positive sequence system also corresponds to swing component measured value C of reactive power quantity Q' of the positive sequence system.
  • a current quantity i' of the positive sequence system is formed according to equation (5): ##EQU3## measured current quantity i, corresponding to swing component value C in current quantity i' of the positive sequence system, is formed from this current quantity, using the signal model given above, by least squares estimate in module 14.
  • Resistance values Wr and reactance values Wx of the positive sequence system are obtained by forming the quotients in quotient forming devices 6 and 9: ##EQU4## these values are then processed in analyzer unit 16.
  • the estimation method calculates coefficients A, B and C of the signal model given in equation (3) above from a limited signal segment of the sampled space vector.
  • This model formulation supplies the amplitude of the estimated space vector component through parameter C.
  • Terms with parameters A and B simulate the 50 Hz components formed by aperiodic components.
  • the amplitude of the 50 Hz oscillation decays with time constant ⁇ of the summated impedance ##EQU5## when this consideration is based on a single-pole equivalent circuit diagram of a power supply line supplied by two equivalent machines and having two equivalent impedances.
  • equation (11) is solved for parameter vector ⁇ k
  • equation (13) is obtained for determining the parameter vector, whose substitution into the signal model according to equation (3) leads to the best simulation of the measured signal in the sense of the least squares.
  • the trajectory test is subdivided into a monotony test and a test for an abrupt signal change.
  • the monotony test checks the course of positive sequence system resistance values Wr which follow one another chronologically for monotony. This test is performed only when oscillation has not yet been detected--the trajectory of the positive sequence system impedance values Z (formed from Wr and Wx) has not yet reached oscillation polygon PPOL (see FIG. 3) because with a synchronous oscillation, the monotony condition would be violated at the point of reversal on the trajectory of the oscillation.
  • the only check performed is to determine whether the chronologically successive positive sequence system resistance values Wr of the positive sequence system impedance vector have a minimum rate of change. If the positive sequence system impedance vector remains the same during a detected oscillation, it can no longer be an oscillation.
  • FIG. 2 illustrates the reversal of the criteria for the monotony test.
  • the monotony test is performed over a suitable selected number N of curve points.
  • N The following criterion is used:
  • the test for a minimum rate of change uses a threshold value to be established for the change in resistance of the positive sequence system within a sampling interval.
  • Measured resistance and reactance values Wr and Wx of the positive sequence system are differentiated for the trajectory test by a first-order method:
  • the test described here permits differentiation between rapid transient phenomena and oscillations. To prevent unwanted operation of the oscillation detection, when oscillation is suspected, a test is also performed to determine whether the trajectory of (R, X), which has been recognized as smooth still has features indicative of a steadily unstable system state.
  • the characteristic curve of the impedance measured at the installation site of a protective device operating by the method according to the present invention is used.
  • the tip of the measured impedance vector at the relay installation site describes an ellipse with a center point on the imaginary axis as a trajectory.
  • the top part of the ellipse is passed through at angle differences up to max. +90°.
  • the bottom part of the ellipse is passed through only at rotor differential angles within the range -90° ⁇ 180° ⁇ +90°.
  • FIG. 3 illustrates this state of affairs.
  • the derivations for the trajectory test are formed by a second-order method:
  • Signal M as an oscillation confirmation signal thus becomes active when a steadily unstable curve point has been identified.
  • Number N of curve points used for the estimate is to be defined in a suitable manner.
  • the only curve points used to estimate the center point are those where the Wr/Wx ratio is below a threshold value to be defined. This minimizes measurement errors in determination of the center of circle.
  • the curve points for which the above-mentioned requirement is met characterize curve segments with an extremely flat shape. If less than two curve points are suitable for estimating the center of the circle, it can be assumed that the entire curve has an extremely flat shape. Such a curve shape is obtained with system oscillations when the synchronous generated voltages of the two equivalent machines are approximately the same. Thus, in this case, a steadily unstable system state can also be assumed. Oscillation confirmation signal M is also active in this case.
  • FIG. 4 shows the center points determined in synchronous oscillation.
  • FIG. 4 shows clearly that a trajectory center point which would indicate a stable operating point in the R-X plane is estimated at the reversal point.
  • the test for unstable curve point is performed only until an oscillation has been detected, i.e., the trajectory has entered oscillation polygon PPOL. Since only a successful test for unstable curve point can lead to detection of oscillation, this test can be omitted during oscillation that has already been recognized. Since the test for an unstable curve point is performed only when the monotony test and the test for abrupt changes in impedance vector have been concluded successfully, discontinuities in the trajectory segment to be tested can be ruled out.
  • FIG. 5 shows calculated active power quantity P' and calculated reactive power quantity Q' of the positive sequence system over time t in the event of a three-phase fault.
  • the influence of the 50 Hz component in the event of a fault occurring at time T can be seen clearly.
  • the curves of measured active power quantity P and measured reactive power quantity Q of the positive sequence system are improved significantly in the same fault case due to elimination of the 50 Hz components by least squares estimators 5 and 8 according to FIG. 1.
  • FIG. 6 shows a power supply system after a three-phase fault as a result of which oscillations occur after detection of a fault.
  • the calculations performed using quantities P and Q and positive sequence system current i lead to a trajectory of values Wr and Wx of the positive sequence system impedance, as shown in FIG. 7, where Z1 denotes the tripping polygon of an internal zone and Z2 denotes the tripping polygon of an external zone of a respective impedance protection device.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
US09/170,889 1997-10-15 1998-10-13 Method of deriving a signal indicating an oscillation in an electric power supply system Expired - Lifetime US6104182A (en)

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DE19746719A DE19746719C1 (de) 1997-10-15 1997-10-15 Verfahren zum Gewinnen eines eine Pendelung in einem elektrischen Energieversorgungsnetz anzeigenden Signals
DE19746719 1997-10-15

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Cited By (17)

* Cited by examiner, † Cited by third party
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US6778919B1 (en) * 1999-09-30 2004-08-17 Siemens Aktiengesellschaft Method for identification of an oscillation in an electrical power supply system
US20050187726A1 (en) * 2003-06-21 2005-08-25 Abb Research Ltd. Detecting electromechanical oscillations in power systems
US20080100043A1 (en) * 2006-11-01 2008-05-01 Autoliv Development Ab Side airbag module with an internal guide fin
US20080281437A1 (en) * 2005-10-31 2008-11-13 Abb Research Ltd Initializing an estimation of dynamic model parameters
US20110102952A1 (en) * 2008-06-26 2011-05-05 Siemens Aktiengesellschaft Method for production of an oscillating signal and of an electrical protection device or measurement instrument having an oscillation identification device
US20110197389A1 (en) * 2010-02-12 2011-08-18 Makita Corporation Electric tool powered by a plurality of battery packs and adapter therefor
US20120173892A1 (en) * 2010-12-30 2012-07-05 Hon Hai Precision Industry Co.,Ltd. Computer motherboard and cpu voltage regulator power supply layout method
US20150051850A1 (en) * 2013-08-16 2015-02-19 General Electric Company Systems and methods for swing angle estimation in an electrical power system
RU2543934C1 (ru) * 2014-04-03 2015-03-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Иркутский государственный технический университет" (ФГБОУ ВПО "ИрГТУ") Способ идентификации типа искажения гармонических сигналов и определения параметров искажения при мультипликативном воздействии (варианты)
CN105530219A (zh) * 2014-09-28 2016-04-27 腾讯科技（深圳）有限公司 一种连接检测方法及装置
WO2017129492A1 (en) * 2016-01-26 2017-08-03 General Electric Technology Gmbh Oscillations in electrical power networks
US10436823B2 (en) 2013-08-16 2019-10-08 General Electric Company Systems and methods for swing angle estimation in an electrical power system
CN112384813A (zh) * 2018-07-06 2021-02-19 乌本产权有限公司 用于识别供电网中的低频振荡的风能系统和方法
US20210139042A1 (en) * 2019-11-08 2021-05-13 Ree Technology Gmbh Autonomous vehicle interface using bus impedance to identify control units, and associated systems and methods
CN113239531A (zh) * 2021-05-07 2021-08-10 南京国电南自维美德自动化有限公司 阻抗保护振荡闭锁判别方法、系统、存储介质及计算设备
US11293996B2 (en) 2019-10-25 2022-04-05 Siemens Aktiengesellschaft Method and device for generating a classification signal classifying an electrical impedance
CN114441899A (zh) * 2022-01-27 2022-05-06 中国电力科学研究院有限公司 电网宽频振荡监测点部署方法、系统、设备及存储介质

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US20100315198A1 (en) * 2008-01-24 2010-12-16 Siemens Aktiengesellschaft Field device and method of operation thereof
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CN104950196A (zh) * 2015-04-30 2015-09-30 中国电力科学研究院 一种识别电力系统振荡中心的复合判据方法
WO2018128188A1 (ja) 2017-01-06 2018-07-12 エーザイ・アール・アンド・ディー・マネジメント株式会社 容器

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US6778919B1 (en) * 1999-09-30 2004-08-17 Siemens Aktiengesellschaft Method for identification of an oscillation in an electrical power supply system
US20050187726A1 (en) * 2003-06-21 2005-08-25 Abb Research Ltd. Detecting electromechanical oscillations in power systems
US7149637B2 (en) * 2003-06-21 2006-12-12 Abb Research Ltd Detecting electromechanical oscillations in power systems
US20080281437A1 (en) * 2005-10-31 2008-11-13 Abb Research Ltd Initializing an estimation of dynamic model parameters
US7912589B2 (en) * 2005-10-31 2011-03-22 Abb Research Ltd Initializing an estimation of dynamic model parameters
US20080100043A1 (en) * 2006-11-01 2008-05-01 Autoliv Development Ab Side airbag module with an internal guide fin
US20110102952A1 (en) * 2008-06-26 2011-05-05 Siemens Aktiengesellschaft Method for production of an oscillating signal and of an electrical protection device or measurement instrument having an oscillation identification device
US8451570B2 (en) * 2008-06-26 2013-05-28 Siemens Aktiengesellshaft Method for production of an oscillating signal and of an electrical protection device or measurement instrument having an oscillation identification device
US20110197389A1 (en) * 2010-02-12 2011-08-18 Makita Corporation Electric tool powered by a plurality of battery packs and adapter therefor
US20120173892A1 (en) * 2010-12-30 2012-07-05 Hon Hai Precision Industry Co.,Ltd. Computer motherboard and cpu voltage regulator power supply layout method
US8739106B2 (en) * 2010-12-30 2014-05-27 Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. Computer motherboard and CPU voltage regulator power supply layout method
US20150051850A1 (en) * 2013-08-16 2015-02-19 General Electric Company Systems and methods for swing angle estimation in an electrical power system
US10024920B2 (en) * 2013-08-16 2018-07-17 General Electric Company Systems and methods for swing angle estimation in an electrical power system
US10436823B2 (en) 2013-08-16 2019-10-08 General Electric Company Systems and methods for swing angle estimation in an electrical power system
RU2543934C1 (ru) * 2014-04-03 2015-03-10 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Иркутский государственный технический университет" (ФГБОУ ВПО "ИрГТУ") Способ идентификации типа искажения гармонических сигналов и определения параметров искажения при мультипликативном воздействии (варианты)
CN105530219A (zh) * 2014-09-28 2016-04-27 腾讯科技（深圳）有限公司 一种连接检测方法及装置
CN105530219B (zh) * 2014-09-28 2019-12-10 腾讯科技（深圳）有限公司 一种连接检测方法及装置
WO2017129492A1 (en) * 2016-01-26 2017-08-03 General Electric Technology Gmbh Oscillations in electrical power networks
CN108604793A (zh) * 2016-01-26 2018-09-28 通用电器技术有限公司 电力网络中的振荡
US11025065B2 (en) * 2016-01-26 2021-06-01 General Electric Technology Gmbh Oscillations in electrical power networks
CN112384813A (zh) * 2018-07-06 2021-02-19 乌本产权有限公司 用于识别供电网中的低频振荡的风能系统和方法
US11293996B2 (en) 2019-10-25 2022-04-05 Siemens Aktiengesellschaft Method and device for generating a classification signal classifying an electrical impedance
US20210139042A1 (en) * 2019-11-08 2021-05-13 Ree Technology Gmbh Autonomous vehicle interface using bus impedance to identify control units, and associated systems and methods
US11840211B2 (en) * 2019-11-08 2023-12-12 Vay Technology Gmbh Autonomous vehicle interface using bus impedance to identify control units, and associated systems and methods
CN113239531A (zh) * 2021-05-07 2021-08-10 南京国电南自维美德自动化有限公司 阻抗保护振荡闭锁判别方法、系统、存储介质及计算设备
CN114441899A (zh) * 2022-01-27 2022-05-06 中国电力科学研究院有限公司 电网宽频振荡监测点部署方法、系统、设备及存储介质

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